This invention relates to an apparatus for and a method of mounting a chip on a circuit board by compression-bonding.
In one conventional method of mounting a chip with bumps, such as a flip chip, on a substrate or circuit board, the bumps are pressed against electrodes of a circuit pattern, formed on a surface of the board, and are connected thereto. In this method, it is necessary to strictly control the value of a load, applied to each bump, as well as a load distribution for each bump, and there is known a method in which when compression-bonding the chip to the board, a compression-bonding load value is measured, and the load is applied while comparing this load value with a target load value. Load measurement means, such as a load cell, is used for this load measurement, and is incorporated in a mechanism of the chip compression-bonding apparatus for transmitting the compression-bonding load.
In the above conventional method, however, the load measurement means is arranged serially in the load transmission mechanism, and a compression-bonding tool, which is pressed through the load measurement means, is held by a spring or the like, and therefore there has been encountered a problem that it is difficult to accurately measure a very small load.
A load sensor, such as a load cell, for measuring a load value requires a certain degree of response time, and also a signal transmission delay is involved in a control system. Therefore, during the time period from inputting of the measured value into a control portion to outputting of a new instruction from the control portion, a downward movement of the compression-bonding tool is obliged to be stopped, and the downward movement and the stop for measurement are alternately repeated little by little. As a result, the downward movement at high speed can not be realized, and the tact time can not be reduced, which leads to a problem that the efficiency of mounting of chips can not be enhanced.